Valorization of <i>Kappaphycus alvarezii</i> via Microwave-Assisted Pyrolysis: A Sustainable Route to Bio-Oil with Antibacterial Properties, Computational Modeling, and Molecular Dynamics Simulations

Bioactive compounds from seaweeds can be harvested and used in a variety of biorefineries, even though seaweeds’ prospective uses in biorefineries are still in the early stages. In the present study, microwave-assisted pyrolysis of seaweed, Kappaphycus alvarezii, yielded bio-oil (17.20 ± 0.25%), biogas (24.20 ± 0.15%), and biochar (58.5 ± 0.40%). The bio-oil characterization via a gas chromatograph/mass spectrometer demonstrated the presence of furan derivatives, like furfural, 1-(5-methyl-2-furanyl)-ethanone, 2,5-furandicarboxaldehyde, and 5-methyl-2-furancarboxaldehyde, and benzene derivatives (phenol and p-cresol) as the major organics. Antibacterial efficacy of bio-oil was tested against pathogenic bacteria, Vibrio parahemolyticus, using in vitro techniques such as zone of inhibition, growth kinetics, and electron microscopy. It was observed that the bacterial pathogen was highly susceptible to the antibacterial action of seaweed bio-oil, and it was evident that the inhibition increased linearly with an increase in concentration of the bio-oil. For molecular insights, the major organic compounds were investigated for molecular docking against significant toxin and thermostable target proteins of V. parahemolyticus, which demonstrated the highest docking scores of −5.0 kcal/mol for toxin proteins and −5.1 kcal/mol for thermostable proteins. Additionally, 100 ns molecular dynamics simulations were performed to investigate the stability, binding energy, and interaction patterns of the furan and benzene derivatives within the active site of the target proteins. Experimental findings were corroborated by computation, which revealed that certain constituents of the bio-oil strongly and stably interacted with bacterial proteins and thus were potential natural antibacterial agents. These results aid in the development of new methodologies for both preventing and managing infections caused by V. parahemolyticus.